Sonothrombolysis (STL) is an emerging non-invasive stroke treatment modality in which ultrasound and microbubbles are used to lyse the clot causing the occlusion in acute ischemic strokes. In these treatments, ultrasound (used to both image/locate the occlusion in the brain vasculature and treat it), is applied via appropriate probes, typically positioned on the patients' temporal bone/window. The temporal bone provides acoustic access to the brain with the smallest amount of signal attenuation and aberration. During these treatments (which could last up to 2 hours), it is important to maintain the position and orientation of the ultrasound probes fixed and directed at the occlusion location for best treatment. Probes are typically held in place against the patients' temporal bone via a headset.
STL uses ultrasound targeting the clot, microbubbles (in systemic circulation), and sometimes a thrombolytic drug such as t-PA (tissue plasminogen activator, a “clot-busting” agent), to break up the fibrin structures that make up a typical clot, so as to try to restore normal blood flow to the occluded region in the brain. Currently, clinical trials are ongoing in sonothrombolysis, using either a combination of (i) ultrasound and t-PA or (ii) ultrasound, t-PA, and microbubbles.
Such treatments typically use head-mounted, single-element transducer(s)/probes to deliver the ultrasound through the temporal bone, operate in continuous or pulsed mode, and typically do not have the ability to target the ultrasound beam, other than using manual positioning of the ultrasound probes mounted in a headframe. The ability to more precisely orient the beam toward a blood clot is overcome by placing many single-element probes on the patients skull, with the expectation that at least one of the beams is aligned and targeting the clot.
Commonly-assigned United States Patent Application No. 2010/0160779 to Browning et al. features a conventional safety helmet for blood clot lysis. The helmet is configured for keeping a pair of ultrasound probes in contact with the temporal regions of both sides of the head. A liner inside the helmet wraps around a circumference of the head. With the probes positioned inside the liner, the liner functions as a transcranial headset. The probes have matrix arrays usable for electronic steering. The probes are utilizable for imaging or therapy, including imaging guidance for steering a therapy beam. Once it is seen, via the imaging guidance, that the probes are suitably positioned, the helmet liner headset can be adjustably secured in place by an adjustment knob.